Hobbing machine



ll Shee'ts-Sheet l O. E. STAPLES HOBBING MACHINE c 395 270 27 7gg 417 July 20, 1954 Filed April 16. 1948 l p 255 Il u I l/ HIIH I \\|\\U\\\\\ W av 2 Il W WIW 005 7.5 0 JMWWJWWW July 20, 1954 o. E. STAPLES 2684,01@

HOBBING MACHINE July 20, 1954 o, E STAPLES 2,684,016

HOBBING MACHINE Filed April 16, 1948 1l Sheets-Sheet 3 /'raRNsys July 20, 1954 0, E; STAPLES 2,684,015

HOBBING MACHINE Filed April 16, 1948 ll Sheets-Sheet 4 i5 |l 4^ 7M\ :i l/l t' I I; I 4//4 J l 120 a "4 l: 721 E f4? INVENTOR. ,475, 5 BY 0775 ".A 5TH/Las MEW fW/m W rraemsvs uly 20, 1954 o. E. STAPLES 2,684,016

HOBBING MACHINE Filed April 16. 1948' ll Sheets-Sheet 5 i "I @Milk 4 lll/111111117 INVENTOR.

f7@ 6 Urfa E. MPM-5 July 20, 1954 o. E. STAPLES HOBBING MACHINE 1l Sheets-Sheet 6 Filed April 16. /1948 JNVENTOR. 077s E. 5m/@L65 ,4free/ways o. E. s'rAPLl-:s 2,684,016

HOBBING MACHINE ll Sheets-Sheet '7 Jllly 20, 1954 Filed April 16, 194e .INVENToR 077.5 I .firma/ E5 BY ,www

July 20, 1954 Q E. STAPLES 2,684,016

HOBBING MACHINE IINVENTOR. Y r/s .5TH/L55 /4 free/ve ys July 20, 1954 Filed April 16. 1948 O. E. STAPLES HOBBING MACHINE l1 Sheets-Sheet 9 INVENTOR. Or/.s E; .5V-wmf@ 7' rae/ve ya July 20, 1954 o. E. STAPLES Hwa/ways l1 Sheets-Sheet l0 July 20, 1954 o. E. STAPLES 2,684,016

HOBBING MACHINE Filed April 16. 1948 11 sheets-sheet 11 Patented July 20, 1954 Zatlt HOBBING MACHINE Otis E. Staples, Euclid, Ghio, assignor to The Cleveland Hobbing Machine Company, Euclid, 1Ohio, a corporation of Ohio Application April 16, 1948, Serial No. 21,493

13 Claims.

The present invention relates to machine tools and, more particularly, to a hobbing machine having means for producing in-feed of the hob relative to the Work.

An object of the invention is the provision of a novel means for producing in-feed of the cutting tool of a gear cutting or hobbing machine, which means may be either incorporated in the machine when built or attached to existing machines Without the necessity of extensive modications thereof.

Another object of the invention is the provision of an improved gear cutting or hobbing machine having means for producing in-feed 01' the cutting tool or hob, which means comprises a mechanical interconnection between the movable supports for the tool and work spindles whereby the in-feed of the tool is accurately controlled by the relative movement between the tool and work spindle longitudinally of the axis oi the latter.

A further object of the invention is the provision of an improved gear cutting or hobbing machine having means for producing in-feed of the cutting tool or hob, which means comprises nuid pressure means continuously urging the tool spindle to move in a direction extending transversely of the work spindle and means carried by the support for the work spindle, and operating by virtue of the relative Vertical movement between the tool and work spindles, to control the movement of the tool spindle in response to the action of the iiuid pressure means and to move said 'tool spindle in the reverse direction in opposition to the action of said iiuid pressure means.

The invention further resides in certain novel features of construction, and combinations and arrangements of parts, and further objects and advantages thereof will be apparent to those skilled in the art to which it pertains from the following description of the present preferred embodiment thereof described with reference to the accompanying drawings in which similar reference characters represent corresponding parts throughout the several views, and in which:

Fig. 1 is a perspective view of a rotatable turrettype hobbing machine embodying the present preferred form of the invention, certain portions being broken away and 4others omitted for the purpose of clarity;

Fig. 2 is an enlarged, fragmentary view of the machine shown in Fig. 1, the View being partly in section and partly in elevation with the section being taken approximately on the centerline 2 of .the machine, the novel in-feed mechanism being shown in side elevation;

Fig. 3 is an enlarged sectional view of hob head and associated parts shown in Fig. 2 illustrating the drive for the tool or hob and the drive for feeding and rotating the work spindle of one unit of the machine;

Fig. 4 is a Vertical sectional View through the lower portion oi the work head illustrated in Fig. 2, the view being taken substantially on the lines 4 4 of Figs. 2 and 7;

Fig. 5 is a side view, partly in section and partly in elevation, of the rapid traverse mechanism for a single unit of the machine, the section being taken substantially on the line 5-5 of Fig. 6 and an additional portion of the housing being broken away to show portions of the rapid traverse motor and associated brake;

Fig. 6 is a top View of the rapid traverse mechanism illustrated in Fig. 5 with portions broken away to more clearly show the construction;

Fig. 7 is a sectional view through the lower portion of the work head, the view being taken substantially on the irregular section indicating line l-T of Fig. 4, with certain parts broken away to more clearly illustrate the gearing connections;

Fig. 8 is a fragmentary sectional view through one of the tailstock supporting means, the View being taken substantially on the line 8-8 of Fig. 1;

Fig. 9 is a sectional view through one of the fluid operated tailstock mechanisms and a portion of the tailstock supporting means, the section being taken substantially on the section indicating line 9.-9 of Fig. 8;

Fig. 10 is a bottom elevational view of one of the tailstock mechanisms, only a portion of the tailstock supporting means illustrated in Fig. 8 being shown;

Fig. 11 is an enlarged, fragmentary, front elevational view of one of the tool or hob heads of the machine and of the novel in-feed mechanism attached thereto;

Fig. 12 is a detached, side elevational View of that portion of the novel in-feed mechanism which is connected with a tool or hob head;

Fig. 13 is an enlarged sectional View, taken substantially on the section indicating line lt-l 3 of Fig. 12, with the actuating arm removed and showing the connection of a portion of the infeed mechanism to the tool or hob head which is controlled thereby;

Fig. 14 is an enlarged, fragmentary, sectional View taken substantially on the section indicating line llt-I4 of Fig. 12.

Fig. 15 is a detached, side elevational view of the siide assembly forming a part of the novel in-feed mechanism, the connections therewith to other portions of the mechanism being indicated in dot-dash lines;

Fig. 16 is a top elevational view of the portions of the mechanism illustrated in full lines in Fig.

Fig. 17 is a fragmentary, side elevational view of a portion of the interior of the machine adjacent the top thereof illustrating the stationary cam for actuating a switch mounted on the back of each unit of the machine;

Fig. 18 is a fragmentary view, partly in side elevation and partly in section,- illustrating the air distributing means and one set of collector ringsl mounted at the top of the machine;

Fig. 19 is a fragmentary front elevational view of one of the fluid pressure control means for controlling actuation of the clutch illustrated in Figs. 2 and 3;

Fig. 2G is a longitudinalsectional View through one of the tool or hob heads with certain members shown in elevation;

Fig. 2l is a sectional viewsubstantially on the line Zl--i of Fig. 20;

Fig. 22 is a fragmentary front elevational view ofthe top portion of one of` the work heads of the machine illustratedin Fig. 1 showing, in dotted lines, certain of the switches` operated by movement of the work head.;

Fig. 23 isa fragmentary side View of the top portion of one of the work heads of' the machine, the view being partly in elevation and partly in section and representing the right-hand. side of Fig. 22;

Fig. 24. is a fragmentary top plan view of a portion of the housing for the'collectorY rings illustrated in Figs. 2 and 3l, the cover plate .for the brushes being removed; and

Fig. 25 is a simplified Wiring diagram of a portion of the electrical-circuits for the machine.

The invention is illustrated' as embodied in al rotatable turret type hobbing machine similar to that illustrated'in U1 S. Patentl 2,629,291, issued February 24, 1953, onA my copending application, Serial No. 757,256, filed June26, 1947', in which many of the novel features hereinillustrated and described are specifically claimed.

The general nature of the machine is illus'- trated in Fig. l of the drawings and' comprises a stationary frame A onf which a turret B is mounted for rotation in the direction indicated by the arrow R. At spaced" points about the turret are mounted a plurality of identical tool or hob heads C and adjacent each tool head the turret carries a work head D, the latter being slidably supported for verticall movement relative to the corresponding tool head. Each tool head is provided with mechanism for supporting and rotating a hobor other tool, the tool being adapted to be rota-ted about an axis extending transversely of the verticali movement of the adjacent work head. In addition; each tool head C includes mechanismv for'producingv a relatively slow axial movement of" the hob or other tool while the latter is rotating. Each work head includes a means Ev forv supporting and rotating a workpiece about a substantially vertical axis, and mechanism F for producing a feeding movement of the work headvertically during a cutting operation. This rotation of vthe workpiece andthe feeding movement thereof are in timed relationship to the rotation of thehob or other tool. The machine also. includes a rapid traverse mechanism G foreach work head to move the latter at a rapid rate to bring the work into cutting relationship with the hob or other tool and to return the work head to its initial position after the cutting operation has been completed. Each tool, or hob head, work head, work gripping means and rapid traverse mechanism, which are associated together, form an operational or hobbing unit and are, at times, so referred to in the subsequent description and the subjoined claims. In addition to these mechanisms, each operational unit of the machine is provided with a novel mechanism H for producing movement of the hob head transversely of the vertical movement of the work head under positive mechanical control of the l tter` This movement ofthe hob head is termed in-feed and. while not limited thereto, is especially useful. when employing the machine to cut gears on cam shafts or the like.

in operating the machine, they turret thereof is rotated so that thev tool and work heads suocessively pass a denite position known as the loading station where workpieces may be in'- scrted removed, the hobbing or other machining o'. eration being effected as the turret continues .'o rotate` and is completed by the time a given operational unity has returned to the loading ion. As will hereinafter appear, the novel in-reed mechanism automatically causes in-feedy oi the hob or other cutt'mg tool of each unit at a predetermined timev during the rotation of the turret. This is eected by a rneclianical interconnection between the movable supports for the tool and work spindles of each unit so that the in-feed. is accurately controlled by the relative vertical movement between the spindles.

Referring now in more detail to. the drawings,

Figs. i and 2 illustrate the frameA as comprising a base 3i! and a central, vertically extending column 3i uniting with the base and forming the main support for the machine. The turret B is rotatably supported upon the column and base by bearings 32, 33', and 3d. Rotation of the turret B is effected by means of a motor 35 which operates through a suitable reduction gearing 36 to rotate a worm 3i and thereby drive the worin vheel 33, which is of large diameter may be integral with or attached to a flange member 39. lThe member 39 is secured by bolts, or other suitable means, to the lower part of a vertically extending annular ineniber fil), which forms the main frameof the turret B.

Each of the tool or hob heads C comprises a tool or hob spindle @i rotatably supported by a spindle supporting member 42, which is in turn carried by a slid'able head member 43 (see also Fig. 3). Each spindle supporting member i2 is angularly adjustable, relative to its head member QS, about an axis normal to the axis of tho hob spindle and is secured to the head member 43 in any adjusted position by bolts M, the heads of which engage within circular' or arcuate T-shaped openings d5. in the front face of the member 43. The head members 43 are slid'ably supported by horizontal ways 48 on the turret member 40, the head members being moved therealong in timed relationship with the vertical movement of the corresponding work head as hereinafter described.

Each of the work heads D is provided with a work holding and rotating means E which includes a work spindle 41 (see Fig. 4) rotatably supported in the lower portion 48' of the work head by antifriction bearings 49, 5|) and- 5l. The

upper end of each work spindle is provided with a chuck and each work head is further provided with a tail slide 52, slidably supported by ways 53 on the vertical portion 54 of the work head D, the several slides 52 each being held in any adjusted position on the Ways by suitable clamping means 55 which are illustrated as comprising conventional clamping plates and bolts. The head members D are slidably supported on vertical ways 56, provided on the turret member 40, and on vertical ways 51, provided on a cap member 53 which is integral with, or secured to, the top of the turret member 40 in any suitable manner. vertically along the ways 56 and 51 by mechanism to be hereinafter described.

The tool and work spindles, 4| and 41, respectively, are rotated in predetermined timed relationship by a motor 59, hereinafter referred to as the cut motor, which is supported upon an adjustable platform 60 on top of the column 3|. This motor is operatively connected to a shaft 6| through a flexible drive 62, the shaft 6| being connected by suitable gearing mechanism, contained within the housing 63 forming a part of the column 3|, to a sleeve 64 which is rotatably supported by bearings 65 on the vertical column 3|. A bevel gear 65 is attached to the lower end of the sleeve 55, by means of bolts or the like, and the gear 66 meshes with a plurality of spaced bevel pinions 61, there being one bevel pinion 61 for each bobbing unit. Each pinion 51 is keyed to a short shaft 68 (see Fig. 3) which is rotatably supported by bearings 69 and 10 in the rear portion of a twopart housing 1| attached to the member 49 and cap portion 58 of the turret B adjacent the edges of an opening therethrough. The drives for the various hobbing units from the gear 55 through the gears 61 are duplicates and, therefore, only one will be described in detail.

As shown in Fig. 3, the forward portion of the housing 1| extends into the hollow interior of the head member 43 and this portion of the housing is provided with an internal shoulder or flange 12 to the rear of which is connected a sleeve member 13. A shaft 14 is journalled in the sleeve member 13 and extends forwardly and rearwardly therebeyond, this shaft being selectively, operatively connected with the shaft 68 by means of a friction plate clutch 15. This clutch is of conventional design and comprises a driving member 15, connected to the shaft 68, and a driven member 11 which is connected to the shaft 1li. The cooperating faces of the members 16 and 11 are provided with friction material 18 and 19, respectively, and are normally forced into engagement by a plurality of spaced compression coil springs Bil exerting force between the rear of the driven member 11 and a housing member lll connected with the driving member.

The housing member 8| is provided with a plurality of axially extending rods 82 which are slidably received in bosses integral with the rear face of the driven member 11, only one rod and cooperating boss being shown. Pivoted to each rod 82 is a radially extending actuating lever 83 which is urged to the illustrated position by the The work head members D are moved action of the springs 80 on the driven member 11 cent the shaft 14 and are adapted to be rocked in a counterclockwise direction by an annular member 94 which is rotatably supported upon a collar 35 slidably supported upon the sleeve 13. The collar is straddled by the bifurcated lower end of an actuating member or lever 85, the forn ward faces of the bifurcated portion bearing against a cooperating surface on the sleeve 85. The lever 8G is pivoted intermediate its ends to a bracket member 81 which is mounted in an opene ing in the forward portion of the housing 1|.

The upper end of lever 86 is pivotally connested to a rod 88 which has an adjustable connection 89 with a piston rod 99. The piston rod 99 extends into a cylinder 9| which is supported upon the cap member 58 or the turret by means of a plate 92 having a depending bracket 93. The inner end of the piston rod 9! is provided with a piston 9d which is adapted to be actuated to the right, as shown in Fig. 3 by fluid pressure admitted to the rear end of the cylinder through a flexible pipe or hose 95, the forward portion of the cylinder being provided with an exhaust port, not shown, communicating the area in front of the piston with the atmosphere.

The ilow of fluid under pressure to the cylinder 9| is controlled by a two-way valve 9S (see Figs. l and 19) mounted upon the cap member 58 of the turret B. As shown in Fig. 1.9, the pipe or hose 95 is connected to this valve 95 which is also provided with a iiuid pressure supply pipe or hose 91 and an exhaust port 98, the latter having an adjustable orifice, such as a needle valve or the like, controlled by an adjusting screw e9. The movable member of the valve 99 is connected by an actuating member or rod les to the armature of an electrically operated solenoid 16|, the valve being so formed that when the solenoid is energized communication is established between the iluid supply pipe or hose 91 and the pipe or hose 95 thus supplying duid pressure to the cylinder 9|. Consequently, the piston 9s is forced to the right, as viewed in Fig, 3, rocking the lever 86 clockwise. This causes the coliar d5 and ari-- nular member 84 to move axially to the left rocking the levers 83, and the lower ends of the latter force the driven member 11 to the right, against the action of the springs Ele, disengaging the clutch.

When the solenoid lill is deenergiaed the movable member of the valve 95 is actuated to inten rupt the communication between pipes or hoses 91 and 95 and to establish communication bem tween the pipe or hose 95 and the exhaust port e8. Hence, the springs 89 of the clutch act through the driven member 11, levers annular member 84 and collar 85 to rock the lever 9S in a counterclockwise direction, this action being assisted by a compression spring |932 mounted upon the bracket 81 and bearing against the lever 85 above its pivot. The counterclockwise movement or the lever (i6 moves the piston. Si@ to the left, as viewed in Fig. 3, thus discharging the fluid the cylinder 9| through the pipe or hose 95, valve 95 and the exhaust port 58. The adjustable orifice the port 93 controls the rate of discharge ci the uid and hence the rate of engagement of the driven member 11 of the clutch with the driving member 16, under the action of the springs Si), thus preventing grabbing. The manner in which the solenoid is energized and deenergized during the working cycle of the machine to eiect operation of the clutch 15 will be hereinafter described.

A bevel gear |93, provided with an integral .the ends of the flatter, the sleeve |94 being jour- 'nalled by bearings H35 in the shoulder 'l2 of forward portion of the housing 1|. The sleeve |613, and hence the gear |33, are held against axial displacement by a nut it, threaded upon a reduced end of the sleeve and engaging the adiacent end of the inner race for the bearings iBS.

The outer end of ythe shaft 'F4 is splined and provided with a bevel gear |97 which is slidably keyed to the spiined portion of the shaft. The gear di is provided with an integral sleeve portion which is rotatably supported in a member t9 by bearings iid, the gear being held against longitudinal displacement relative to its bearings by a nut il! threaded upon the sleeve portion ll nd the member les being attached to the spindle suppor .ng member The outer face of the gear lo? preferably p1. vided with a cylindrical member il?. which surrounds the outer end of shaft T4 to protect the latter.

The bevel gear iii?, meshes with a bevel geen.` l I3 connected with the upper end of a vertical shaft H41, the latter being journalled by bearings 55 in opening in the lower side of the forward por 'on of the housing 'E'.i. This shaft l e forms a part of the work spindle rotating and feeding mechanism, which will be subsequently described in detail. The gear lill' is in mesh with another bevel. gear HG mounted` upon a shaft il? and forming part of the drive for rotating and axially moving the tool or hob spindle i. lt will. be apparent therefore, that when the clutch l5 is enge d, the shaft 'M will be rotated by the cut motor S' through the gears t5, i3?, shaft |58, and clutch 'i5 thus driving the shaft l E6 for rotating feeding the work spindle, as hereinafter described, the shaft ii? also being rotated for rotating and axially moving the tool spindle. Conversely, disengagement of the clutch i5 interrupts rotation of the shaft "J4 simultaneously stepping the mechanism driven thereby.

As shown in Fig. 4, the lower end of shaft i ie is splined and passes through a helical gear H8 which is keyed to the splined portion of the shaft Sli to be rotated thereby, the splining permitting the gear to be slid axially along the shaft. The gear H3 is positioned within a housing its, attached to the lower portion i8 of the work head D, the gear being prevented from displacement relative to the housing by means of anut and 'washer assembly |2t^= which engage one side of the inner race for the antifriction bearings |2| in which the shaft lit is journalled, the other side of the inner race of these hearings being in engagement with. a shoulder formed a sleevelike portion of the gear lill. The lower end of the shaft Elfi extends into -ore of the housing l |9 and is journallcd by antriiiction hearings |22, which are positioned between cylindrical sleeve extension. of the gear i i3 and the enlarged upper end of the aforementioned bore in the housing H9.

The helical gear l i8 meshes with another helical gear |23 mounted upon a stub shaft |25, the latter being journalled in a portion of the housing i is by means of antifriction bearing 525, |26 (see 7). The gear |23 is also in mesh with a helical gear |21 which is keyed to one end of a shaft |28, the latter being rotatably supported by antifriction bearings |29, |33 in the housing HS and in the portion 48 of the work head, respectively. The other end of the shaft i2@ carries a spur gear i3| for rotation therewith, and the gear |3| meshes with a spur gear |32 rotatably mounted upon a stub Ashaft |33, the latter being supported by a bracket |34 connected with the portion 48 of the work head. The shaft |33 is also provided with a spur gear |35, connected to rotate with the spur gear |32, and the gear |35 meshes with a spur gear v|36 keyed to one end of a worm shaft |31 the latter being journalled by suitable antifriction bearings i3d and |39 in a sleevelike support i4@ mounted in the portion 48 of the work head D. Intermediate its ends, and within the interior of the portion d8 of the work head, the shaft |37 carries a worm Mi which meshes with worin wheel |42 secured to the worl: spindie 4i. Therefore, when the clutch 'I5 is engaged, the motor 59 will effect rotation of shaft ||4 thereby rotating the work spindle 4'! through the gears H8, |23, |21, ISI, 32, |36, worm |4| and worin wheel M2.

The end of the worm shaft |31, opposite to the end on. which is attached the gear |35, is provided with a pinion 143 which meshes with a. gear |44 rotatably mounted upon a stub shaft M5, the latter being supported by a bracket |45 connected to portion 43 of the lwork. head. The shaft |45 also supports a gear i4? which is mounted to rotate with the gear |45. The gear Hi? meshes with a gear |48 which is keyed to a shaft It, this shaft being journalled by antifriction bearings |53 and y|Eii in the por-tion 4i) of the work head D. The inner end of the shaft l-i'ii is provided with a worm |52, which drives a worm wheel |53 forming a part of a feed nut As shown in Fig. 4, the feed nut |54 comprises a cylindrical sleevelike extension of the worm wheel |53 and is internally threaded to cooperate with the threads on a feed screw or shaft 55. rEhe sleeve-like portion of the feed nut is journalled in a suitable bore-like opening within the portion 48 of the work head member Aby antifriction bearings |56 and iii?, the nut being held against axial displacement relative to its bearings by means of an integral shoulder' cooperating with bearing |56 and a nut |58 cooperating with the bearing |51.

The bore in which the feed nut and screw are located may be closed by a suitable cap |58 to prevent the entrance of dirt, chips or the like.

The construction is such that when the clutch 75 is engaged, the motor 59 will drive the shaft H4 thereby rotating the worin shaft |31, in the manner previously described, and this rotation of the shaft |37 operates through the gears |43, |44, |47', 'm3, worin |52, and worm wheel |53, forming a part of the feed nut |54, to cause the latter to rotate relative to the feed screw or shaft |55. Since the feed nut |54 is supported against axial movement, this rotation. causes the said not, and hence the entire work head, to move vertically as the nut threads along the screw or shaft |55. As previously mentioned, the lower end of the shaft IM is splined so that the gear may move therealong during this operation. Moreover, the rotation of the work spindle fl?, the vertical movement thereof, are in predetermined timed relationship and may be simultaneously started and stopped by the operation of the single clutch 15. This vertical movement of the worl: head and work spindle is that which is commonly known as a feeding movement and is effected at a relatively sloaT rate while the hob or other tool supported upon the spindle 4| performs a cutting or bobbing operation upon the work carried by the work spindle 41.

Each work head D may be rapidly moved in a vertical direction by means of a separate rapid traverse mechanism `Ci- (see Figs. 5 and 6) which includes a motor |68, the shaft -|6| of which is connected to a worm shaft |62 upon which is mounted a worm |93. The worm |63 cooperates with a worm wheel |611 connected for rotation with the lower end of the feed screw or shaft |55, the lower end of the latter being supported by suitable antifriction bearings y|65 and |66 in the housing for the rapid traverse mechanism Hence, when the motor |80 is rotated, the feed screw |55 is rotated relative to the feed nut |54, thereby causing vertical movement of the work head D at a relatively rapid rate, hereinafter' referred to as rapid traverse. The motor |89 is preferably reversible and its shaft |\S|, or the worm shaft |52 connected thereto, is provided with an electrically operated brake |81 which is spring actuated to normally engage the shaft for preventing rotation of the latter and of the feed screw |55, the brake being provided with an electromagnet which releases the brake when energized. It will be observed that there is a separate rapid travers-e motor |69 for each of the work heads carried by the machine so that the rapid traverse movement of each work head is independent of that of all the others. The vertical movement of the work heads is selectively effected at either the feed rate by motor 59, or at the rapid traverse rate by motor |88, as determined by actuation of switches in an electrical circuit hereinafter descri-bed.

Each of the work heads D of the machine is provided with a fluid operated work holding means E for securing a workpiece to the work spindle. In the illustrated machine, this means comprises an internal chuck |88 secured to the upper end of the work spindle t1 for rotation therewith. As shown in Fig. 4, the body of this chuck and the work spindle 41 are provided with aligned bores through which a chuck actuating rod |89 extends, the upper end of the rod being provided with an enlarged portion having a substantially conical surface |18 slidable within a counterbore provided at the upper end of the chuck. Extending radially outward through the side walls of the upper portion of the chuck are a plurality of work-gripping ngers'l 1| the ngers being slidable radially and Ihaving inclined camming surfaces on their inner ends for cooperation with the conical surface |18. The construction is such that, when the rod |59 is moved downwardly within the chuck |88, the fing-ers |19 are forced radially outwardly to engage a workpiece W and securely hold the latter.

Movement of the rod 189 is effected by a fluid operated means which comprises -a cylinder |12 attached to the lower portion 48 of the work head D by a suitable plate or bracket |13. The lower end of the rod |69 extends within `the cylinder |12 and is provided therein with a piston, not shown, which is adapted to be moved vertically in either direction by uid under pressure supplied through pipes or hoses y|18 and |15, which are connected to a source of iiuid under pressure in a manner hereinafter described. Hence, when fluid pressure is allowed to enter the cylinder |12 through one of the pipes, the rod |99 is lowered thereby actuating the fingers |111 into workgripping position. Reversing the direction of application of iluid pressure to the pipes |14 and |15, and hence to the cylinder |12., elevates the rod |89 thereby releasing the lingers |1| and freeing the work for ready removal. The internal construction of the fluid operated means. generally designated as a cylinder |12, is substantially like that employed for the tail stock mechanism about to be described.

Referring now to Figs. 2, 8, 9 and 10, it will be seen that the tail stock mechanism for each unit of the machine, generally designated |16, is supported by the tail slide 52 upon the ways 58 of the vertical portion 54 of work head D, the tail slide being provided with clamping plates and screws 55 cooperating with the ways 53 (see Fig. 8) so that the tail slide and the tail stock mechanism may be moved along the ways to a desired position and secured to the ways at that position. The tail slide 52 is provided, on its outer end, with a bore in which is positioned the lower, reduced diameter portion |11 of a cylinder |18 which forms the main body of the tail stock mechanism. This lower portion |11 of the cylinder is provided with one or more longitudinally extending tapered slots or grooves, such as |19 and |80, at spaced points on that side thereof which is adjacent the work head, and tapered gibs or Wedges |8| and |82 are inserted in the tapered grooves |19 and |88, respectively, to cooperate with the bore of the tail slide 52 and thereby clamp the lower portion |11 of the cylinder therein.

rfhe tapered gibs or wedges are actuated by screws |83 and |84 which are threaded into the upper wall of a recess provided in the lower surface of the tail slide 52, these screws each being provided with an enlarged integral collar or washer |85, |86 which fits in a slotted opening in the side of the corresponding gib or wedge |8| and |82. Hence, when the said screws |83 and |86 are threaded inwardly, they carry the wedges or gibs upwardly, as viewed in Fig. 9, thus rmly gripping the portion |11 of the cylinder |18 and retaining the latter in proper position Within the tail slide 52. A retainer |81 is provided in the tail slide 52, below the gibs or wedges |8|, |82 to prevent the latter from dropping out of the slide if the screws |83 or |84 should be disengaged from their threaded bores. A suitable collar or Washer |88 may be provided between a shoulder on the cylinder |18 and the top surface of the slide member 52, if desired, to provide a predetermined spacial relationship between the cylinder and the tool slide.

A piston rod |89 extends from the hollow interior of the cylinder |18 through an aligned bore in the lower portion |11. Adjacent its upper end, the piston rod is provided with a piston plate |98, which is illustrated as being integral with the piston rod and having a sliding t Within the interior of the cylinder |18. Piston packings |9| and |92 are provided upon the upper and lower surfaces of the piston plate, respectively, and retained thereon by rings |93 and itil, respectively, which are connected to the piston plate |98 by screws |95 and |96, respectively. There is thus provided a fluid-tight piston which moves downwardly within the cylinder when uid under pressure is supplied through an opening |91 in the cover plate |98, exhaust being effected through an opening |99 in the lower side of the cylinder below the piston. The piston is moved upwardly Within the cylinder when luid pressure is supplied through the opening |99, the opening |91 then acting as the exhaust. A sealing means 288 is provided in the bottom of the cylinder |18 and cooperates with the piston rod |89 to prevent the leakage of uid thereabout.

The lower end of the piston rod |89 is longitudinally bored for a considerable distance, and within this bore is inserted a tail center 20|. The upper end of the tail center is recessed and 11 provided with a ball 202 for cooperation with a wear plate 203 provided at the inner end of the bore in the piston rod, the ball 202 and wear plate 2&3 permitting substantially frictionless rotation of the tail center relative to the piston rod. rihe tail center 20| is provided with an annular groove 202 with which the reduced diameter, inner end of a set screw 225 cooperates, the head of the screw being ilush with or countersunk below the outer surface of the piston rod ISS so as not to interfere with the sliding of the latter within the bore of the cylindrical portion Ill. The tail center 20| is also preferably provided with a helical lubricating groove 22E communicating with aligned lubricating openings in the slide 52 and the portion Ill oi the tail stock, an oil cup 207 being screwed into these openings.

It will be apparent, from the construction just described, that when the piston is moved downwardly by the application of fluid pressure to the opening |92, the piston rod |09 moves the tail center 2d! into engagement with the upper end of a workpiece clamped upon the chuck ist. The tail stock will remain in nrm engagement with the workpiece throughout the machining operation by virtue of the rluid pressure acting upon the piston, rotation of the tail center with the workpiece being per iitted by the rotatable mounting oi the tail center in the hollow bore in the lower end of the piston rod. When the machining operation has been completed, the application of fluid pressure to the opening |09 and the use of the opening i9? as the exhaust, moves the piston and piston rod upwardly withdrawing the tail center Ztl :trom engagement with the workpiece so that the latter may be removed, it being remembered that the workgripping Fingers ii of the chuck are also released at this time.

The tail slide 52 for mounting the uid pressure operated tail stock may be of substantially solid consti .ction or may be formed as a relatively hollow member constructed similar to those illustrated in U, S. Patents Nos. 2,292,260 and 2,231,856. A mounting of the latter type is here d'sclosed to reveal how such tail slides may be modied to incorporate the illustrated tail stock mechanism. As shown in Fig. 3, the tail slide comprises a casting in which are formed suitable Ways for cooperation with the vertical ways 53 of the portion 5t or" the work head D. The tail slide is further provided with a transversely extending bore 208 within one end of which is positioned a pinion 209 formed upon the inner end of a substantially cylindrical mem ber 2i, ri'he member 2|0 has a central bore through which passes a bolt 2| the outer end oi the latter being provided with a substantially cylindrical locking member 2|2. The locking member 2i2 has a tapered inner surface cooperating with a correspondingly tapered inner surface on a second cylindrical member 2|3 which is positioned within a bore 2id extending substantially transversely of the bore 208. A bolt 2|5, having a headed portion resting in a slotted opening in the vertical portion 54 of the Work head D, extends outwardly through the cylindrim cal member 2 i3 and is provided on its outer end with suitable nuts 2|0. The outer end of the bolt 2l! is likewise provided with nuts 2|1. It will be seen, therefore, that when the nuts 2i@ and 2H are tightened, the members 2|2 and 2 i3 will be locked in engagement and the bolt 2|5 will clamp these members, and hence the slide 52, to the vertical portion 54 of the work head.

12 This clamping is further assisted by the previously described clamping means which comprise suitable plates and screws cooperating with the vertical ways 53.

The interlocking oi the members 2i?. and 2i3 position the pinion 2&9 for cooperation with a vertical rack 2 i8 attached to the vertical portion oi the work head by suitable screws 210. By slightly loosening the nuts 2| and the clamping means 55 and by rotating the member 2id, the pinion 269 thereon causes the tail slide 52 to move vertically with respect to the work head member by virtue of the cooperation between the pinion 209 and the teeth of the rack 2|8. When the tail slide has reached the desired position the clamping means may be re-tightened to retain the tail slide in its adjusted position.

In the tail slide mechanisms of the aforemcn tioned patents there was no provision for vertical movement of the tail center relative to the tail slide, and hence a rack and pinion arrangement, similar to that just mentioned, for adjusting the tail slide was necessary to secure the proper en gagement of the tail center with the work. Therefore, an operating handle was provided for the member 2id. In the orin oi the tail stock, herein disclosed, it is no longer necessary to move the tail slide to effect engagement and release or" each workpiece, since the tail center is now moved vertically by fluid pressure to engagement with the work and subsequent lease therefrom. Hence, the tail slide need only be adjusted once for each size of work and this adjustment need not be made with great exactitude. It follows that the rack 2|@ the co operating pinion mechanism are no longer nec essary, since adjustment of the slide may be effected by simply loosening the clamping means and manually moving the tail slide upon the ways. He ce, when the tail slide mechanisms the aforementioned patents are to be converted for use with the iluid operated tail stock herein disclosed, the reduced cylindrical portion Ili oi' the latter is simply inserted within the cylin drical opening provided in the tail slide 52 oi the prior art type of tail center, and the operating handle for the rack and pinion mechanism is then replaced by a simple disk or cover plate such as 220, the rack 2|() being omitted or left in place as desired since it no longer has any necessary function in the device.

In accordance with this invention, a novel mechanism is provided for moving each hob or tool head towards and away from the cooperating work head in timed relationship with the vertical movements oi the latter, thereby causing in-feed of the hob or other tool to perform the desired hobbing or other machining operation and automatic return of the hob or other tool to its initial position after the desired operation has been completed. The mechanism for effect-- in this movement for each oi the hob heads is the same and hence only one such mechanism will be described in detail.

As shown in Figs. l, 2 and 1l thr ugh i6, the present preferred form of this mechanism includes a substantially channel-shaped member' 22i which is secured to one side oi the slidable member 43 of the tool head by means ci bolts 222 and drive pins 223, a suitable spacer 22d, or plurality of spacers, being interposed between the members i3 and 22| where necessary due to the shape oi the former so that the web oi the member 22| is rigidly held in substantially vertical plane. A member 225 is slidably supported asegure by the legs and the web of this channel member, the sliding member being prevented from displacement, other than sliding movement, by gibs 226 and 221, attached to the legs of the channel. member and cooperating with horizontally extending recesses in the front face of the member 225 adjacent the upper and lower edges of the latter. The slioe member 225 is also provided with a longitudinally extending bore 228, extending therein from the right-hand side there of, as viewed in Fig. l2, and within this bore is positioned a sleeve nut 225 which is held from rotation and axial movement by drive pin 23?)l cooperating with a flattened side of the nut or passing through a secantly disposed slot or hole therein. Screwed into the sleeve nut 225 is one end of an adjusting screw 23| which is rotatably supported, adjacent its other end, by an end plate 232 secured to the forward end of the channel member, the screw 23| being held from longitudinal displacement by any suitable means.

In the construction shown, longitudinal displacement of the screw 23| is provided by an integral collar 233 provided upon the screw and cooperating with one side of the end plate 232. Forwardly of the collar, a non-threaded portion of the screw is journalled in the end plate, and adjacent the forward face of the end plate the screw is threaded and provided with a lock nut 232, the lock nut in turn having a set screw 235 to prevent loosening of the lock nut. The forward end of the adjusting screw 23| is provided with a polygonally shaped portion 236 to receive a wrench or other tool by which the adjusting screw may be turned to thereby adjust the position oi the sliding member 225 relative to the channel member 22|. The extent of this adjustment is indicated by a calibrated dial 231, which is secured to the screw between the polygonally shaped portion and the lock nut, the indicia on the dial cooperating with a mark or arrow upon the end plate 232.

One end of a link 238 is pivotally secured to the slide member 225 adjacent the inner end of the latter, the left-hand end as viewed in Figs. l2 and 14, by means of a stud bolt or the like 239. The other end of the link 238 is pivotally connected to the lower arm 245 of a bell crank lever, generally designated 24|, by means of a stud or the like 242. This bell crank lever is pivoted intermediate its ends to a bracket 243, which is secured in a manner hereinafter described, to the annular member 45 of the turret B. The other arm 244 of the bell crank lever has its outer or upper end pivotally connected to the bifurcated lower portion of a. threaded rod 245, the threaded portion of which is screwed into an adjusting sleeve 245, the bore of the latter being provided with oppositely directed threads in the upper and lower portions thereof. Threaded into the upper end of the adjusting sleeve 245 is the threaded lower end of a piston rod 231, the threads of which extend in the opposite direction to the threads on the rod 245. The upper end of the piston rod 241 is connected with a piston 248 slidable within a cylinder 249. This cylinder is pivotally mounted upon the cap member 53 of the turret B by means of a bracket 25|) which has a depending ear 25| received between spaced, upwardly extending ears 252 and 253 attached to, or integral with, the upper end of the cylinder 249, a suitable pivot pin or the like 254 passing through aligned openings in the ears 25|, 252 and 253. The cylinder 246 is adapted to have 'i tending to cause uid pressure supplied thereto through an operiing adjacent the bottom thereof by means of a pipe or conduit 255 so that the fluid under pressure thus admitted to the cylinder acts upon the piston 248 to urge the latter upwardly, any fluid above the piston being exhausted through a port not shown.

The construction thus far described isA such that fluid pressure applied to the cylinder 249 through the pipe or conduit 255 acts upon the piston and through the piston rod 241 to rock the bell crank lever 24| in a counterclockwise direction, as viewed in Figs. 2 and 12. This rocking of the lever 24| tends to move the slide member 225 to the right, as viewed in Figs. 2 and l2, and since the slide member `225 is connected to the channel member 22| by the screw 23|, and since the channel member is in turn connected with the sliding head member 43, this rocking movement of lever 24| tends to move the head member 43 oi the hob head forwardly, that is to the right, as viewed in 1Eig. 2. Hence, the movable portion of the hob head is urged or biased in the direction of the work head thus in-feed of the hobbing spindle and of the hob or other tool attached thereto. Movement of the tool or hob head in the direction just mentioned is, however, positively controlled by a cam carried by the cooperating work head D, as hereinafter described, so that in-feed of the hob or other tool is effected only in exact predetermined relationship with the vertical movement of the work head. The force with which the head member 43 is urged inwardly as just mentioned may be adjusted by adjusting the sleeve member 246, thereby varying the effective leverage of the bell crank lever 24|, while the initial and iinal positions of the tool or hob head upon its ways 46, and hence the position of the tool relative to the work, may be adjusted by turning the adjusting screw 23|.

The lower portion 46 of the work head D is provided with a bracket 256 into which is screwed the threaded lower end of a cam supporting shaft 251. The threaded upper end of shaft 251 is screwed into an enlarged boss 258 which is integral with, or attached to, a substantially vertical extending cam plate 255. The shaft 251 is provided with a polygonally shaped portion 265 intermediate its ends by which the shaft may be rotated and thereby adjust the elevae tion of the cam plate relative to the bracket 256, it being understood that the opposite ends of the shaft 251 are provided with oppositely directed threads. The threaded portions of the shaft 251 are provided with jam nuts 26| and 262 for cooperation with the bracket 256 and boss 253, respectively, tc thereby lock the shaft 251 in its adjusted position.

The cam plate 253 is supported for vertically sliding movement by a plate-like member 263, the lower end of which is connected to a bracket 264 which is in turn connected to the adjacent vertical way 56 for the lower portion i8 of the work head D. As will be seen from Fig. 15, this plate-like member 263 is provided substantially centrally thereof with a substantially rectangularly shaped opening through which the boss 258 freely extends so that the shaft 252 is disposed on one side of the plate 263 while the cam plate 253 is disposed on the other side of the plate 253, the construction being such that the cam plate 253 extends closely adjacent the front face ofthe slide member 225 adjacent the Aforward or right-hand end thereof as viewed .in

Figs. 2, 12 and l5. The cam plate25-9 is provided with a suitable cam surface, which is here illustrated as comprising .an elongated opening 285 with a forwardly extending .recess or offset adjacent its lower end, and within this opening 265 is received a cam roller 258 vrotatably mounted upon the slide member 225. The cam plate 259 is guided in its vertical movements by means of gibs 261 and 268, `attached to rearwardly extending shoulders on the platelike member adjacent the longitudinal edges thereof, which gibs cooperate with suitable recesses in the cam plate 259 so as .to form guideways for the latter, as is clearly shown in Fig. 16.

As mentioned above, the application of iiuid pressure through the pipe or conduit 255 to the cylinder 2122 exerts force upon the movable portion i3 of the tool or hob head C in a direction tending to move the latter, and hence the tool or hob spindle ffii, toward the work spindle carried by the work head so that the cam roller 26S is held in positive engagement with the forward edge of the cam shaft 265. When the work head is in its lowermost position, however, the cam roller 2&5 upon the slide 255 will'be positioned in the upper end or the .cam slot or opening 255 in the cam plate 259 and hence the hob or tool head is prevented from moving forwardly under the action of the fluid pressure applied to the cylinder 249. As the work head D moves vertically upwardly the enlarged or recessed portion of the cam slot 265 will eventual-1y come opposite the cam roller 266 and, since the roller is constantly urged against the .forward edge of the cani slot 265, the hob head will then be moved forwardly, or to the right as viewed lin Figs. 2, l2 and l5, under the force exerted by the pressure iiuid in the cylinder 249. The cam slot recess is so designed that this movement .of the tool head provides the desired amount of infeed. Additional vertical movement of the work head D occurs after this in-feed movement of the hob head, as will be seen from Fig. 15, during which additional vertical movement the hobbing oi the workpiece is effected. It will be understood that the relative dimensions of the several portions oi the cam slot 225 which are shown are simply illustrative of the one embodiment of the device and that these dimensions maybe changed tc eiect greater or less vertical movement of the work head before the in-feed occurs and/or greater movement of the work head in its infed position.

Prior to the time that the lower end of the slot 255 engages the cam roller 256 the upward vertical leeding movement of the work head is discontinued by means hereinafter described and the work head is then returned to its initial position. During this return the cam plate 259 now moves downwardly so that the slot 255 forces the tool or hob head away from the work spindle, or to the left as viewed in Figs. 2 and l5, it being understood that this movement is in a direction opposite to that in which the tool or hob head is urged by the fluid pressure applied to the cylinder 22e so that the cam roller 256 is always in positive engagement with the cooperating'cam surface in the slot 225 and hence the hob head is moved in either direction in exact predetermined relationship with the movement of the work head. The rearward movement of the tool or hob head acts through the mechanism -connected between the latter and the piston -24'8 to 1s move the .latter against the fluid pressure ap'- plied to the .cylinder 249.

During .thenormal `operation of the machine, iluid pressure is continuously applied to the cylinder 249 Vso that the cam roller 255 is at all times infirm engagement with the forward edge of the cam slot 265. It is not necessary, however, that this biasing of the hob head in the direction of the work head be effected exactly as here illustrated ,and described. For example, a suitable spring may be substituted for the cylinder 22S. Moreover, either a spring or pressure operated device could be connected drectly with the slide member 225 rather than through the disclosed lever system.

The iluidpressure for operating the clutch, the tail center and the chuck mechanisms and for exerting force to move the tool or hob head in the in-feed direction may be either hydraulic or pneumatic andmay be supplied from any suitable source such as a reservoir and pump mounted in the :base of the machine. As shown in the drawings, however, air pressure is utilized and is supplied to the machine from an outside source of supply `such as the air line commonly provided in .factories for cleaning purposes or the like. The air pressure is conducted .from such a supply to the machine at the top thereof through a stationary pipe 265 (see Figs. 1 and 18). This pipe has a vertical extending portion 21|] substantially in alignment with the vertical axis of the machine and the lower end thereof is journalled in a .rotatable air distributing chest 22|. This chest is supported above the motor 58 by a spider-like framework .212 having radially extending arms 213.connected with vertically extending frame members .214 which extend upwardly from the turret cap member 58 and are circumferentially spaced thereabout. Hence, the chest v21| rotates with the turret when the rotation motor 35 is energized. rlhe air distributing chest 21| is provided with a plurality of radially extending pipes 21.5 for conducting the air pressure from the Ychest to each operational unit of the machine. Since all of the operational units of the machine are identical the air distribution from only one of the pipes 215 will be described.

The pipe 215 of each unit is connected to one end of a flexible conduit or hose 216 the other end of which is connected by a T 211 to the pipe or hose 218, and toa pipe or hose 219. The pipe or hose 218 is connected by a T 28D to the fluid pressure supply line 9.1 for the valve 96, which controls the operation of the clutch for the unit,

and to the pipe or conduit 255 connected to the cylinder 249 of lthe in-feed mechanism. The pipe 219 is connected 'to a solenoid operated twoway valve 28|, the solenoid 232 of which is energized by an electrical current iowing in a cable 283 extending to a suitable outlet 284 upon the cap member 58 of the machines turret. From the valve 28| a pipe or hose 285 extends vertically downward adjacent the vertical portion of the work head D, the lower end of the pipe being connected with a T 286 Yfrom which a pipe or hose 281 extends to a pressure regulator '283; From the lower end of the pressure regulator, the previously mentioned pipe or hose |14 extends to the upper connection for the cylinder |12 of the fluid pressure operated chuck. A branch pipe or hose 289 extends from the T 286 to the upper opening |91 of the fluid pressure operated tail stock.

From the lower portion of valve 28|, a pipe for hose 290 leads vertically downward adjacent the portion 54 of the work head D, the lower end of this pipe or hose terminating in a T 29| to which is connected a pressure regulator 292 from which a branch pipe or hose 293 leads to the side exhaust opening |99 in the fluid operated tail stock. Also connected to the T 29| is one end of the previously mentioned pipe or hose |15, the other end of which is connected to the cylinder' i12 for the iiuid operated chuck.

The valve 28| is so constructed that when the solenoid 282 is deenergized the valve is positioned to cause fluid pressure from the pipe or hose 216 to communicate with the pipe 285, the pipe 290 being vented to the atmosphere through the valve. When the solenoid 282 is energized the valve 28| is operated to apply uid pressure to the pipe 290, the pipe 235 then being vented to the atmosphere. It follows, therefore, that when the solenoid is deenergized the valve 28| causes fluid pressure to be supplied through the pipes 285, 281, and |14 to the cylinder |12 causing the rod |89 of the chuck |58 to actuate the latter for firmly engaging a workpiece. Fluid pressure is also supplied, through the pipe 289 causing the piston of the tail stock mechanism to be moved downwardly to engage the tail center 20| with the workpiece. Fluid pressure will be maintained in these lines throughout a cutting or hobbing operation, thus holding the parts in their aforementioned positions. When the cutting or hobbing operation is completed, the solenoid 282 is energized, as hereinafter described, actuating the valve 28| to vent the pipes |14, 281, 289 and 285 and to supply fluid pressure through the pipes 298, and 293 thereby releasing the chuck and -.i

actuating the tail center in a reverse direction to release the workpiece.

Since the chuck and tail center are held in work gripping positions by air pressure, a failure of the supply of air pressure to the pipe 269 would partially release the work with consequent damage thereto and to the hob or tool T if the latter is operating upon the work. Also, since the clutch is held in its disengaged position and the tool or hob head is continuously urged towards the work spindle by air pressure, a failure of the supply of these mechanisms would allow the clutch to improperly engage and would also cause improper operation of the in-feed mechanism. To prevent such conditions from occurring, the pipe 259 is provided with a pressure responsive electrical switch 294 (see Fig. l). This switch is normally closed but if the air pressure drops below a predetermined value the switch opens thus stopping the entire machine as will become apparent from the subsequent description of the electrical circuit for the machine.

The machine is provided with a coolant system for supplying a cutting or cooling liquid to the hobs or tools during a machining or hobbin-g operation. The coolant or cutting liquid is supplied from a reservoir within the base of the machine by means of a pump, not shown, and by a conduit 295 and a pipe or pipes 296 to a trough reservoir which is not shown but which is located in the cap member 58 of the rotatable turrret. Equally spaced pipes 291, one for each unit, conduct the coolant or cutting liquid from the trough to valves 298, and to each of the latter is connected a pipe 299 (see Fig. 1). The lower end of each pipe 299 is provided with a nozzle 300 adjacent the hob or tool spindle 4| of the unit and so directed that the coolant or cutting fluid will flow over the hob or other tool and the work being cut thereby, the liquid being returned to the base of the machine by gravity for cleaning and further circulation. The valve 298, between the pipes 291 and 29% for each unit, is electrically operated and is controlled in a manner, hereinafter described, such that coolant is allowed to flow only when a cutting operation is being performed and is automatically terminated when the cutting operation has been completed. Lubrication for the machine is provided by a circulating system of conventional design, the vertical supply pipe 38| of which extends through the hollow turret (see Fig. 2).

Referring now to Fig. 20, it will be seen 'that the spindle supporting member 42 is provided with an outboard bearing support 392 and an inboard bearing support 383, the latter preferably being integral with the member ft2. The bearing support 382 is provided with a non-rotatable sleeve bearing or bushing 38d and the bearing support 393 is provided with spaced antifriction bearings 385 and 388, the spindle il being journalled in the bearings for rotation and axial sliding by means of sleeves 321 and 388. The sleeve 301 both rotates and slides with the spindle 4| relative to the bushing 384 while the sleeve 388 rotates but is prevented from sliding relative to the bearings 385 and 385 by an integral shoulder 309 and by the mechanism connected thereto which is hereinafter described.

The spindle di has a shoulder Sl intermediate its ends for engaging one side face of a hob or other tool T, indicated by dot-dash lines in Fig. 20, the sleeve 3811 engaging the other side face of the tool, with the tool and sleeve being held against longitudinal displacement relative to the spindle by means of a nut 3H provided upon the threaded outer end of the spindle fil. in the event the longitudinal extent of the tool T is less than the distance between the inner end of sleeve 381 and the shoulder 3io, as is the situation illustrated in Fig. 20, one or more spacing collars or washers 3|2 may be employed as shown. A keyway 3|3 is provided in the spindle 4| by means of which the tool is keyed to the spindle to prevent relative rotation therebetween.

Attached to the spindle supporting member 42, and to the bearing support 383, is a housing 3|4 containing the mechanism for rotating and axially moving the tool or hob spindle 2|. This mechanism includes a gear M5, disposed within the housing 3M and slidably keyed or otherwise attached for rotation with the spindle 4| and for relative axial movement therebetween. This gear, and hence the spindle, are driven by a gear 3 6 which is fixed upon the outer end of the shaft I1 for rotation with the bevel gear l i6 (see Fig. 3) when the clutch 15 connects shaft 1li for rotation by shaft 88. The gear 3 5 has a cylindrical sleeve-like extension SE1 extending through an opening in an inner wall Siti of the housing 3|4, and the spindle li has a threaded portion 3|9 of reduced diameter extending beyond the outer end of this sleeve extension 3 l1 of the gear 3|5. Screws 328 extend through the sleeve extension 8 1 of gear 8|5 and are threaded into the flange or shoulder 329 of the sleeve 388 thus connecting these members for rotation together.

Screwed upon the inner end of the threaded portion 3|9 of the tool spindle 4| is a sleeve nut 32| the inner end of which is externally flanged. Between the flange of nut 32| and the adjacent end of the sleeve extension SI1 of gear 3|5 is disposed a spacer 322. The sleeve nut 32| is provided with external threads on which is threaded one end of a sleeve 323, the outer end 

